Christian leaders have convened in New Orleans this week to celebrate 100 years of ecumenical cooperation.

More than 400 people from the National Council of Churches and its humanitarian arm, Church World Service, opened the three-day anniversary event on Tuesday with the aim of unifying the church.

"In one sense, this event will be a 'celebration' of modern ecumenism," said NCC General Secretary the Rev. Dr. Michael Kinnamon in a statement. "But it will also [be] a time for assessing the churches’ failure to receive God’s gift of unity, for anticipating new directions for ecumenism in the 21st Century, and for recommitting ourselves and our churches to the ecumenical calling."

The gathering in New Orleans comes months after a global celebratory event in Edinburgh, Scotland. There, hundreds of leaders from across Christian denominations and traditions reaffirmed their commitment to witnessing to Christ as one. They were marking the 100th anniversary of the World Missionary Conference held in Edinburgh in 1910.

While the 1910 conference brought together leaders mainly from the Protestant community, invitations for both the global and U.S. centennial celebrations this year have gone out to those of other traditions including Roman Catholics, and Orthodox and Pentecostal leaders.

"Leaders of various partner bodies – in this effort to realize a visible unity of faith, witness, and service – have indicated their strong interest in participating in this centennial assembly," noted Kinnamon.

Some of the issues participants at this week's event will be discussing are: unity in an age of radical diversity, interfaith relations, the environment, terrorism, and inequality. NCC had formed study groups to compile vision papers on each of these issues. The groups' study documents are not position papers but points from which to dialogue from and to start taking action.

One of the papers proposes that the goal of the ecumenical movement is to celebrate the diversity "of our God-given oneness as the people of God, the body of Christ and the temple of the Holy Spirit." And as the movement enters its next century, it must find new ways of holding unity and diversity "in appropriate and creative relationship."

The document notes that in the early decades of the ecumenical movement, participants were more likely to place emphasis on unity "as if diversity were a problem to be resolved" and to compromise confessional identities. But over the last two generations, more emphasis has been placed on diversity in which churches preserved their historic identities while sharing in sacraments ministry and mission.

"It is not the purpose of this study to argue for or against various models of Christian unity, but rather to suggest that overemphasis on diversity, like overemphasis on unity, can have destructive consequences," the paper points out.

"Churches settle for tolerant cooperation rather than struggling to overcome church dividing issues that prevent eucharistic sharing and the reconciliation of ministries. Instead of valuing diverse individuals as essential to genuine community, the church succumbs to individualistic self-sufficiency that denies the interdependence of Christian women and men. Affirmation of particular identity is too often seen as an end in itself rather than a call to share the Spirit’s gifts in order that Christ’s body may be ‘built up in love’ (Eph 4:16)."

The document further laments ongoing conflicts within churches – not just among churches – over the issue of unity and diversity. While some denominational establishments suppress diversities when invoking unity, others are invoking diversity as justification for departure to alternate church bodies.

Participants are expected to discuss ecumenical cooperation that values both the church's unity and its diversity while acknowledging the "indispensable relationship between them."

The National Council of Churches claims to be the leading force for ecumenical cooperation among Christians in the United States. Its member groups – which include mainline denominations, Baptist churches, Orthodox bodies, and African American and Living Peace churches – represent some 45 million persons across the nation.

NCC's 2010 General Assembly was expanded into a Centennial Ecumenical Gathering. The event concludes Thursday.